Automatic regulating arrangement



April 14, 1931. R. H. LINDSAY 1,800,303

AUTOMATIC REGULATTNG ARRANGEMENT Filed Aug. 26, 1927 E a E2 IN V EN TOR.

[anywa ATTORNEY Patented Apr. 14, 1931 UNITED STATES PATENT OFFICE RUSSELL H. LINDSAY, OF NEW YORK, N. Y., ASSIGNOR T0 AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK AUTOMATIC REGULATIN G ARRANGEMENT Application filed August 26, 1927. Serial No. 215,592.

This invention relates to signaling systems, and particularly to transmission systems employing devices for automatically controlling the energy levels therein.

(5' Circuits for the transmission of voice frequency signals, such as telephone circuits or the like, may undergo variations in attenuation due, for example, to weather changes. Corrections must be applied to such circuits in order to maintain the circuit equivalents substantially constant. One form of regulating arrangement for applying the desired corrections ma consist of two or more vacuum tubes of, or example, the three-electrode type. The grid electrode of such a tube normally is biased negatively with respect to the filament and it controls the electronic emission between the filament and the plate. The rid electrode of such a tube may also be so iased ne atively with respect to the filament that t e electronic emission between the filament and the plate will be practically negligible under normal conditions. Two such tubes may be so biased negatively as to prevent the passage of currents in their respective plate circuits, one or the other of these grid electrodes subsequently becoming less negatively biased with respect to its filament when there is to be an increase or a decrease in the energy flowing in the signaling system.

Accordingly, it is one of the objects of this invention to provide two vacuum tubes, both of which have grid electrodes which may be greatl biased negatively with respect to their laments, and to substantially diminish the negative bias on one or the other of these grid electrodes when the energy control means of a transmission circuit is to be increased or decreased.

It is another object of this invention to couple the energy control means of a transmission circuit to an electrical motor so that when either of the grid electrodes of two three-element vacuum tubes undergoes a substantial diminution in its negative bias, the motor may be set into rotation in one direction or the other to correspondingly vary the energy adjustin means.

It is a further object of this invention to pick up a small portion of the energy flowing from an input circuit into an output circuit, which are interconnected by an energy adjusting means, to rectify the energy so picked up and cause that energy to substantially change the bias on the grid electrode of either of two three-element vacuum tubes,'to accordingly revolve the armature of a motor in one direction or the other and to thereby cause the energy adjusting means to be correspondingly varied.

While this invention will be pointed out with particularity in the appended claims, the invention itself, both as to its further objects and features, will be better understood from the detailed description hereinafter following, when read in connection with the accompanying drawing showing two embodiments of the invention merely for the purpose of illustration.

Referring to Figure 1 of the drawing, an input circuit E is shown connected to the output circuit E through an energy adjusting means G, which may, for example, be a potentiometer, as shown. Alternating current, which may be transmitted for the purpose of actuating the adjusting mechanism, will flow from the input circuit E to the output circuit E in the direction indicated by the arrows. In this invention, the level of the energy of this current in the input circuit may vary within certain limits, and it is desired to keep the level of this energy asapplied to the output circuit within small limits of variation, preferably by automatic means. The potentiometer or energy adjusting means may have sufiicient range of variation upon manual adjustment to properly affect the level of the energy flowing into the output circuit; but in this invention means will be particularly provided for automatically changing the position of the potentiometer or energy adjusting means G in accordance with changes in the level of energy flowing in the transmission circuit.

A motor having an armature A and a field coil F is so related to the system that armature A may be caused to rotate in one directioner or in the other, as found desirable. The field coil F is supplied with current from crably through a train of gears (not shown).

Thus,'when the armature A rotates in one direction, the energy passing through the potentiometer G is increased, and when the armature rotates in the opposite direction,

G is decreased.

Asmall portion of the current transmitted to the output circuit E is. applied to. the

primary winding of a transformer T the impedance of the primary winding being preferably substantially high to thereby limit the amount of energy applied to transformer T .The currentap'plied to the priing of transformer T and condenser C mary winding of this transformer becames similarly applied to the input circuit of a rectifying device which may, for example, be a rectifier tube of the three-electrode type.

- Thus, this energy may be applied between the rid electrode and filament of a rectifier tube V. The filament of tube V is heated to an electron emitting temperature by a battery B A condenser C fshownin dotted 111168 brid es the secondar windin of 7 y transformer T Thus, a tuned circuit is provided which includes the secondary windwhich may be employed for. selectively aplying, between the grid electrode and the filament of the vacuum tube V,current of thefrequency which is to be transmitted; for the purpose of actuating theadjusting mechanism, thus separating this current from other currents of undesired frequencies which may also be transmitted at the same time, such. as, for example, the currents of frequencies directly involved in the transmission of speech. It will be understood, however, that. any other rectifying device may be employed instead ofvacuum tube V, within the scope of this invention. 1 1

tube V The plate circuit of the vacuum includes a meter J, resistances P and P a battery B and the filament and plate of the vacuum tube V. This is adirect current circuit. A by-pass for alternating currents is provided by a condenser G condenser C being connected between the plate and filament of the vacuum tube V. i

The meter J of the direct current circuit may havea dial whichis graduated to indicate whether the energy fiowingv in this circuit is normal, high or low. When normal current flows through meter J, its pointer will rest-1n position N. ,When current of higher magnitude flows therethrough, the

pointer of this meter may reach the H position, and when current lower than normal fiows therethiough, this pointer may reach the L position. Thus, when the pointer of this meter is at its N position, the level of the energy in the output circuit E is normal. When the pointer reaches the H position,

justing means G to become lower and to accordingly' decrease the level of the energy in the output circuit E Qonversely, when the. pointer of meter J reaches the L posivtio'n, the apparatus of this invention will' the energy passing through potentiometer vacuum tubes are heated to electron emitting Y temperatures by the flow of current from a battery B The input circuit of the vacuum tube V includes the grid electrode and filament of the vacuum tube V and the adjustable resistance'P The input circuit 1 of the'vacuum tube V includes the grid electrode and filament 'of the vacuum tube V the adjustable resistance P and a battery B The output circuit of vacuum tube V includes the filament and plate of the L vacuum tube V ,*the winding of relay R and a battery B5. The output circuit of the vacuum tube V includes the filament and theplate of thevacuum tube V the winding of relay R and battery B The battery B is common to both output circuits and maintains the plates of the vacuum tubes V and V at suitable positive potentials. V

fWhennormal current fiows'through the resistances P and P the grid electrodes of vacuum tubes V and V will be biased negatively'with'respect to their correspond ing filaments. Thenegative potential for the grid electrode ofvacuum tube'Vi is derived from the drop in potential across the adjustable resistance 7P while the negative potential for the grid electrode of the vacuum tubeV is derived from the adjustable resistance P and from the battery B Without the presence of battery B the grid electrode'of vacuum tube V would 'normally be biased positively with respect to its filament. The battery B is so poled and I is of. such ,a'voltage that it normally' oposes and overcomes the volta e obtained from the adjustable resistance P thereby biasing the grid electrode of the vacuum tube Pg suitably negative with respect to its filament. Thus, battery B is so connectedthat its: negative terminal faces the gridelectrode, and thisbattery has a greater voltage than the voltage normally derived from the. adjustable resistance P If the level of energy fiowlng in the outice iput circuit E increases, the current rectied by vacuum tube V will also increase and this will be indicated upon the dial of meter J. Moreover, the drops in potential across resistances P and P will increase by corresponding amounts. An increase in the drop in potential across resistance P merely renders the grid electrode of vacuum tube V more negative with respect to its filament and further insures the system against the passage of current t rough the winding of the relay R The increased drop in potential across the resistance P however, will have the effect of reducing the negative potential impressed upon the grid electrode of the vacuum tube V Thus, if this reduction in voltage is suificiently great, current will begin to fiow in the output circuit of the vacuum tube V and if this current reaches a sufficiently high value, i. e., a predetermined value, relay R will become operated. Accordingly, a relay R will be operated, current flowing through the winding of relay R from a battery B through the armature of relay R and its contact. The operation of relay R causes the attraction of its two armatures so that current may flow from battery B through the armature A of the motor, the circuit of armature A of the motor including battery 13,, one of the armatures of relay R armature A of the motor and the other armature of relay R Thus, the motor is revolved in one direction, and, by virtue of the coupling existing between the armature A of the motorand the energy adjustin means G, causes a decrease in the energy owing past the adjusting means G. Yet, the motor continues to operate until the rectified current derived from the output circuit E returns to a value approximating the normal value, the rectified current being then insuflicient to cause the transmission of a current through the winding of relay R sufficient to operate that relay. Hence, relay R. will become released and the motor will stop.

If, on the other hand, the level of the energy in the output circuit E decreases, the current rectified by vacuum tube V will also decrease, and the decrease will be indicated upon the dial of meter J. Accordingly, the drops in potentials across resistances P and P will also decrease. The decrease in the drop in potential across resistance P will merely bias the grid electrode of the vacuum tube V more negatively with respect to its filamentand thereby insure the system against the operation of relay R However, the decreased drop in potential across resistance P may tend to permit the flow of current in the output circuit'of'vacuum tube V and if the decrease in potential across resistance P be sufiiciently great, a current may flow in the output circuit of vacuum tube V of a magnitude sufiicient to cause the operation of relay R Upon the operation of relay R relay R will operate, current flowing through its winding from the battery B through the armature of relay R, and its contact. The operation of relay R will attract its two armatures so that current may flow from battery B through the armature A of the motor, the circuit through armature A of the motor includin battery B-,, one of the armatures of relay armature A of the motor, and the other armature of relay Accordingly, the motor will be started in rotation in the opposite direction. Consequently, the potentiometer of energy adjusting means G will be moved so as to increase the flow of energy, thereby causing an increase in the magnitude of the rectified current of vacuum tube V. The motor A will continue to operate, however, until the magniture of the rectified direct current will be insufficient to maintain relay R in its operative condition. Hence, relay R will be released and the motor will stop.

The H and L positions of meter J indicate the limits at which armature A of the motor is started in rotation in the process of readjusting the energy flowing through po tentiometer spond to definite magnitudes of the resistances P and P These limits may be made wider or narrower by changing the impedance of the resistances P and P Assume, for the sake of illustration, that the drops in potential across resistances P and P are substantially equal, and that the voltage of battery B is normally twice the drop in potential in resistance P Thus, when there is a change in the rectified current as indicated on meter J, the rate of change and the voltage effective upon the grid electrodes of the vacuum tubes V and V will be substantially the same. To decrease the limits H and L at which the adjusting mechanism is to be started in operation, the drop in potential across resistance P should be decreased, while the drop in potential to be effected in resistance P should be increased.

\Vhen this is done, however, the rate of i.

change in the voltage impressed upon the grid electrode of the vacuum tube V with respect to a change in the reading of the meter J will become greater than the rate of change in the voltage impressed upon the grid electrode of the vacuum tube V Consequently, vacuum tube V will become more sensitive to changes in the rectified current, and vacuum tube V less sensitive. On the other hand, if it is desired to increase the limits H and L, the drop in potential to be effected by resistance P should be increased, while the drop in potential in P should be decreased. Thus, there will be an increase in sensitivity in vacuum tube V and a de- G. These limits will correice limits Hand L are to be changed and the sensitivity in both vacuum tubes maintained substantiallyalike while equal voltage drops Will be efiiected by resistances P and P changes may be made inthe setting of resistance'l and accompanied by changes in the voltage of battery vB so that the voltage of battery B may always be substantially twice the voltage derived from resistance P when normal current fiows through meter J. r 7 If the vacuum tube systemv is to have greater sensitivity in response to changes in thejflow of current through the meter J at any particular limitsof operation, such as the H and L limits, it maybe obtained by increasing the magnitudes of resistances P and P cand compensating for the increase in these resistances by additional batteries or other direct current voltages in the.

grid circuits of the respective vacuum tubes. Fig. 240i the drawing shows the grid circuits of the vacuum tubes V and V to whichadditional batteries have been added, battery. B being shown in the grid circuit of the vacuum tube V while battery B, as well as B are in the grid circuit of the vacuum tube V In this embodiment of the invention, the resistances P and P may be set for greater voltage drops. Battery B is connected so that its positive terminal faces the grid electrode ofthe vacuum tube V while the negrtiveterminal of battery B faces the grid electrode of the vacuum tube V This vacuum tube system may be made more sensitive by virtue of the fact that the change in the potential drop across each resistance for a given change of current fiowingtherethrough is proportionate to the magnitude of the resistance, and, therefore, if the magnitude of resistance P or P be made larger, the voltage change upon the grid electrode of the corresponding vacuum tube will be larger for a given change in the magnitude of the rectified current, and the sensitivity of" the systen will be correspondingly increased. The chiefpurpose in adding batteries or other direct current sources to the rid circuits of the vacuum tubes is to maintain the grid electrodes at suitable negative potentials with respect to the corresponding filaments under normal conditions.

While this invention has been pointed out in certain particular embodiments for the purpose of illustratiomit is to be distinctly understood that the general principles of this invention maybe applied to other and "widely varied organizations without departing from the spirit of the invention or the scope of the appended claims.

I V 7 What is claimed is:

Y The combination of an input circuit and an output circuitinterconnected by en ergy adjusting means,-a rotatable device which may be rotated -in either direction, twothree-element vacuum tubes each havinga grid electrode, aplateand a cathode, both grid electrodesbeing so biased negatively -with respect to the corresponding cathodes as to prevent; a substantial flow of current in the corresponding plate circuits, a substantial, flow of current being established in one plate circuit or on the other when the energy applied to said adjusting means materially increases or decreases, respectively, means associated with the plate circuit of the first vacuum tubeto cause the rotation of the rotatable device in one direction when the current in the corresponding plate circuit becomes substantial, and means associated with the plate circuit of the second vacuum tube to cause the rotation of the rotatable device in the opposite direction when the current in the corresponding plate circuit becomes substantial.

2. The combination of two three-element vacuum tubes each having agrid electrode, a plate and a cathode, means for rendering said grid electrodes equally negative with respect to the corresponding cathodes, means for substantially decreasing the negative bias on the grid electrode of the, first vacuum tube, thereby substantially increasing the plate current of that vacuum tube, means for substantially decreasing the negactive basis on the grid electrode of the second vacuum tube, thereby substantially in creasing the plate current of that vacuum tube,,a rotatable device which may be r0 tated in aclockwise direction or in a counter-clockwise direction, means for rotating said device in a clockwise direction when there is a substantial, increased plate currentin the first vacuum tube, and means for rotating said device in a-counter-clockwise direction when there .is a substantial, increased. plate current in the second vacuum tube. j .3. The combination otan input circuit and an output circuit interconnected byenergy adjusting means, a rotatable device coupled to said energy adjusting means which, when rotated in one direction, causes. an increasein the energy flowing through'said adjusting means and, when rotated in the other direction, causes a dec-reaseinthe energy flowing through said adjusting means, a rectifier which .rectifies portion of the energy flowing in said output circuit, two electron tube circuits energized by the rectified current, a substantial current flowing in the plate circuit of one of the electron tubes when the rectified current increases materially, a substantial plate current flowing in the output circuit of the other of the electron tubes when'the rectlfied current decreases materially, means for causing the rotation of the rotatable device in one direction when there is a material increase in the flow of current in the plate circuit of one of the electron tubes, and means for causing the rotation of the rotatable device in the other direction when there is a material increase in the flow of current in the plate circuit of the other of the electron tubes.

4. In combination, an input circuit, an output circuit, a potentiometer interposed between said circuits for controlling the level of the energy of the input circuit applied to the output circuit, a motor coupled to the arm of the potentiometer, a duplex vacuum tube system interconnecting the output circuit and the motor, a portion of the energy of the output circuit being applied to the vacuum tube system, means for effectively energizing one of the paths of the vacuum tube system when the level of the energy impressed thereon rises above a first predetermined limit, means for effectively energizin the other of the paths of the vacuum tu e system when the level of the energy impressed thereon falls below a second predetermined limit, means for rotating the motor in one direction when one of the paths of the vacuum tube system is effectively energized, and means for rotating the motor in the opposite direction when the other of the paths of the vacuum tube system is effectively energized.

5. The combination of an output circuit and an input circuit interconnected by a potentiometer employed to control the level of the energy flowing between the input circuit and the output circuit, a motor mechanically coupled to the potentiometer, means coupled to the output circuit for rectifying only a small portion of the energy applied to the output circuit by the input circuit, means including a first vacuum tube system to rotate the motor in one direction when the level of the rectified energy increases above a first predetermined value, and means including a second vacuum tube system to rotate the motor in the opposite direction when the level of the rectified energy decreases below a second predetermined value, the motor remaining stationary when the level of the rectified energy lies between said first and said second predetermined values.

6. The combination of two three-element vacuum tubes each having a grid electrode, a plate and a cathode, each grid electrode being normally biased highly negative with respect to the corresponding cathode so as to prevent the flow of current in the corresponding plate circuit, a source of rectified current of variable amplitude coupled to the grid electrodes of said vacuum tubes, means whereby one of said grid electrodes will be rendered less negative with respect to the corresponding cathode so as to cause a substantial flow of current in the corresponding plate circuit and the grid electrode of the second vacuum tube will be rendered "more negative, withrespect to its cathode when the amplitude of the rectified current of said source increases beyond a predetermined value, and means whereby the grid electrode of the second vacuum tube will be rendered less negative with respect to its cathode so as to cause a substantial flow of current in the corresponding plate circuit and the grid electrode of the first vacuum tube will be rendered more negative than normally with respect to its cathode when the amplitude of the rectified current of said source decreases below a predetermined value.

7. The combination of two three-element vacuum tubes each having a grid electrode, a plate and a cathode, means including a source of direct current for rendering the grid electrodes in said vacuum tubes equally negative with respect to the corresponding cathodes, said source of direct current being of variable amplitude and being coupled to the grid electrodes of said vacuum tubes,

means whereby the negative bias on the grid electrode of one of the vacuum tubes will be substantially decreased and thenegative bias on the grid electrode of the other vacuum tube will be substantially increased when the amplitude of the current ofvsaid direct current source rises above predetermined value, and means whereby the negative bias on the grid of the first vacuum tube, will be substantially increased and the negative bias on the grid electrode of the second vacuum tube will be substantially decreased when the amplitude of the current from said direct current source drops below a predetermined value.

8. The combination of an input circuit and an output circuit interconnected by energy adjusting means, a rotatable device coupled to said energy adjusting means which when rotated in one direction will cause an increase in the gain of said adjusting means, and, when rotated in the opposite direction, will cause a decrease in the energy flowing through said adjusting means, two three-element vacuum tubes coupled to the output circuit, each vacuum tube having a grid electrode, a plate and a cathode, each grid electrode being normally maintained at a suitable negative potential with respect to the corresponding cathode, means for substantially decreasing the negative bias on the grid electrode of the first vacuum tube so as to cause a substantial increase in the fiow of current in its plate circuit, means for substantially decreasing the negative bias on the grid electrode of the second vacuum tube so as to cause a substantial increase in the flow of current in its pllate circuit, means for rotating the rotate.

1e device in one direction when the "e 7 teases platefcurrent of the first vacuum tube {is substantially increased, and means for ro- 1 tating-said rotatable devicein the opposite direction when the plate current of the second vacuum tube is substantially increased. V v

9. The. combination of first and second three-element vacuum tubes each having a grid electrode, a plate and a cathode, two 1 resistances each of adjustable .magnitude, one associated with each vacuum tube, two sources of direct current potentiahone as sociated' with each vacuum tube, one resistance, and one source of direct current poten- 5 tial being connected to the grid electrode and cathode of each vacuum tube, and a source of rectified current coupled to said resistances, a substantial current flowing in the plate circuit of the first vacuum tube and "a negligible current flowing in the plate circuit of the second vacuum tube when the magnitude of the current flowing fromsaid source of rectified current increases materi- I ally, a substantial current flowing in the plate circuit of the second vacuum tube and a negligible current flowing in the plate circuit of the first vacuum tube when the magnitude of the current flowing from said 7 source ocfr'ectified current decreases materially.

In testimony whereof, I have signed my name to this specification this 24th day of August, 1927. a r V RUSSELL H. "LINDSAY. 

